A secondary battery represented by a lithium secondary battery exhibiting high energy density and operating voltage and excellent charge retention and service-life characteristics has been widely used as an energy source for various electronic products as well as various mobile devices.
Depending upon the kind of an external device in which a secondary battery is used, the secondary battery may be configured to have a detachable type structure in which the secondary battery can be easily inserted into and removed from the external device or to have an embedded type structure in which the secondary battery is embedded in the external device. For example, the secondary battery can be inserted or removed into or from devices, such as laptop computers, as needed. On the other hand, devices, such as some kinds of smart phones and smart pads, require an embedded type battery pack due to the structure or capacity thereof.
Meanwhile, various kinds of combustible materials are contained in the lithium secondary battery. As a result, the lithium secondary battery may be heated or explode due to the overcharge of the lithium secondary battery, the overcurrent in the lithium secondary battery, or other external physical impact applied to the lithium secondary battery. That is, the safety of the lithium secondary battery is very low. For this reason, safety elements, such as a positive temperature coefficient (PTC) element and a protection circuit module (PCM), which are capable of effectively controlling an abnormal state of the lithium secondary battery, such as the overcharge of the lithium secondary battery or the overcurrent in the lithium secondary battery, are connected to a battery cell of the lithium secondary battery.
In general, an embedded type secondary battery pack uses a plate-shaped battery cell, which is suitable for electrical connection, and a PCM is connected to the battery cell via conductive nickel plates by welding or soldering. That is, the nickel plates are connected to electrode terminals of the battery cell by welding or soldering, a flexible printed circuit board (F-PCB) is attached to one side of a double-sided adhesive tape, a protective tape is attached to the other side of the double-sided adhesive tape, and electrode tabs of the F-PCB and the nickel plates are connected to each other by welding in a state in which the F-PCB is in tight contact with the battery cell. In this way, the PCM is connected to the battery cell to manufacture a battery pack.
It is required for the safety elements, including the PCM, to be maintained in electrical connection with the electrode terminals of the battery cell and, at the same time, to be electrically isolated from other parts of the battery cell.
To this end, insulative tapes are attached to various members, including the PCM. In addition, a portion of a sealed part of a battery case, in which the battery cell is received, is bent, and an insulative tape is attached thereto or a barcode is printed thereon. That is, the process is very complicated.
Since a plurality of insulative tapes or parts is required to achieve safe connection as described above, a battery pack assembly process is complicated and manufacturing cost of the battery pack is increased.
In addition, when external impact is applied to the battery pack, the PCM may be damaged or dimensional stability of the battery pack may be greatly lowered due to the use of the insulative tapes, which exhibit low mechanical strength.
Therefore, there is a high necessity for a technology that is capable of reducing the number of members mounted to the battery cell to simplify an assembly process, achieving stable coupling between members loaded on the battery cell, and protecting the PCM.